Project Summary/Abstract Nanosensor-Based Phenotypic Screening for Precision Therapy of Cancer Stem Cells Cancer stem cells (CSCs) have stem cells characteristics, including the ability to self-renew and populate new tumors. These cells are resistant to chemotherapy and are responsible for tumor recurrence and metastasis, making them important yet challenging therapeutic targets. In this U01 proposal, we will use a nanoparticle-based sensor to rapidly phenotype CSCs, using this information to screen for small molecule and nanoparticle therapeutics capable of differentiating CSCs to cells that are less aggressive and more susceptible to chemotherapeutics. Aim 1: Rotello will develop a robust nanoparticle-polymer high throughput-high content screening (HT-HCS) process for discriminating between CSC and non-CSC tumor cell models developed by Mercurio. Aim 2: Rotello will use the HT-HCS platform to identify small molecule and nanoparticle therapeutic agents with selective in vitro toxicity to CSC cells, and Mercurio will validate their ability to impact the in vitro and in vivo behavior of breast cancer cells. Aim 3: Mercurio will isolate CSCs from patient-dervied xenografts (PDX), and Rotello will use the HT-HCS platform to indentify precision therapeutic strategies in vitro that will be tested by Mercurio for their ability to hinder the initiation and recurrence of individual tumors. This ambitious research integrates the cancer biology expertise of Mercurio (UMass Worcester) with the nanomaterials and sensing capabilities of Rotello (UMass Amherst). The research will be greatly facilitated by the complementary team of researchers assembled for the project, as well as the extensive animal capabilities at Worcester and state of the art nanomaterials facilities at Amherst.